Fig. 1. Illumination model of high reflection surface

Fig. 2. Schematic of defect detection device

Fig. 3. Schematic of deflection light in stripe direction

Fig. 4. Schematic of effective detection area

Fig. 5. Images of standard stripe. (a) Stripe image generated by MATLAB; (b) moiré image taken by camera

Fig. 6. Different types of defect samples. (a) Standard surface; (b) sand hole; (c) orange skin; (d) belt marks

Fig. 7. Characterizations of different defects on moiré image. (a) Standard surface; (b) sand hole; (c) orange skin; (d) belt marks

Fig. 8. Stripe image of sand hole defect

Fig. 9. Defect stripe images in different stripe distances. (a) Stripe spacing of 0.25 mm; (b) stripe spacing of 0.50 mm; (c) stripe spacing of 2.00 mm

Fig. 10. Gray distributions of different defects. (a) Standard surface; (b) sand hole; (c) orange skin; (d) belt marks

Fig. 11. Gray distributions of improved fringe images. (a) Standard surface; (b) sand hole; (c) orange skin; (d) belt marks

Fig. 12. Diagram of defect detection algorithm

Fig. 13. Image preprocessing module. (a) Original image; (b) image centerline; (c) corrected image centerline; (d) corrected image

Fig. 14. Processing results of sand hole defect by algorithm. (a) Original image; (b) ROI grayscale image;(c) image after defect enhancement;(d) image after defect feature extraction; (e) morphologically processed image; (f) identification result

Fig. 15. Processing results of belt mark defect by algorithm. (a) Original image; (b) ROI grayscale image;(c) image after defect enhancement;(d) image after defect feature extraction; (e) morphologically processed image; (f) identification result

Fig. 16. Processing results of orange skin defect by algorithm. (a) Original image; (b) ROI grayscale image;(c) image after defect enhancement;(d) image after defect feature extraction; (e) morphologically processed image; (f) identification results

Fig. 17. Defect detection and labeling results. (a) Sand hole; (b) orange skin; (c) belt mark; (d) pit